Process for the preparation of aryldimethylchlorosilane

ABSTRACT

Aryldimethylchlorosilanes, useful as reactive intermediates in organosilicon chemistry, are prepared by reacting a diaryldimethylsilane with an organochlorosilane R4 nSi Cln, where R is an aliphatic or aromatic hydrocarbon group and n 1 or 2, in the presence of aluminium trichloride.

Bazouin et al. Apr. 17, 1973 54 PR CESS FOR THE PREPARATION OF 2,730,540 1/1956 Sauer ..260/448.2 P 2,746,981 5/1956 Wagner 6t a]. ..260/448.2 P

[75] Inventors: Andre Bazouin, Luzinay; Marcel OTHER PUBLICATIONS Lefort Cahm'e both of France Noll, Chemistry and Technology of Silicones, [73] Assignee: Rhone-Poulenc S.A., Paris, France AcademiC Press, P- 58 [22] Filed: P" 1971 Primary ExaminerDaniel E. Wyman [21] Appl' No: 136,567 Assistant ExaminerPaul F Shaver AttorneyStevens, Davis, Miller & Mosher [30] Foreign Application Priority Data 57 BST T Apr. 23, 1970 France ..7014777 Aryldimethylchlorosilanes useful as reactive intermediates in organosilicon chemistry, are prepared by [52] US. Cl ..260/448.2 P reacting a diaryldimethylsilane with an or- [51 Int. Cl. ..C07f 7/08, C07f 7/12 ganochlorosilane R Si Cln, where R is an aliphatic or [58] Field of Search ..260/448.2 P aromatic hydrocarbon group and n l or 2, in the presence of aluminium trichloride. [56] References Cited 6/1951 Clark ..260/448.2 P

I 9 Claims, N0 Drawings PROCESS FOR THE PREPARATION OF ARYLDHVIETHYLCHLOROSILANE The present invention relates to a process for the preparation of an aryldimethylchlorosilane by a redistribution reaction between a diaryldimethylsilane and an organochlorosilane.

This redistribution reaction is advantageous because it makes possible conversion, at little cost, of an organosilicon compound of little practical value into another compound of greater practical value. In particular, it is desirable to convert diaryldimethylsilanes, which are, for example, obtained as by-products in the preparation of dimethylphenylchlorosilane by phenylation of dimethyldichlorosilane, into organosilicon compounds possessing reactive chlorine atoms, because these last mentioned compounds are useful for the preparation of polysiloxane oils.

The present invention provides a process for the preparation of an organosilicon compound of the general formula:

Me Ar-Sil-Cl in which Ar represents a monovalent aromatic hydrocarbon radical wherein an organosilicon compound of the general formula:

lvlle ArSliAr Me (II) in which the radicals Ar, which may be identical or different, each represent a monovalent aromatic hydrocarbon radical, is reacted, in the presence of aluminium chloride, with an organochlorosilane of the general formula:

(4 n n In in which the radicals R, which may be identical or different, each represent monovalent, saturated or unsaturated, hydrocarbon radicals of aliphatic,

cycloaliphatic, aromatic or aralkyl nature, and n is 1 or six carbon atoms.

The reaction can be represented as follows:

If the initial diaryldimethylsilane possesses different radicals Ar, a mixture of dimethylarylchlorosilanes (I) is, in general, obtained; thus one of the preferred embodiments of the invention involves using symmetrical diaryldirnethylsilanes (11). Furthermore, if n is equal to 2, the reaction produces two monochlorosilanes and the use of such reactants is preferred because it allows two reactive organosilicori compounds to be obtained.

The reagents (II) and (III) can be used in any desired proportion. In general, an excess of organochlorosilane (Ill) relative to the stoichiometric requirements of the reaction, as defined above, is added.

The aluminium trichloride can be used in proportions by weight which range from 0.1 to 10 percent and preferably from 0.5 to 5 percent relative to the total weight of organosilicon compounds introduced. Preferably, anhydrous aluminium trichloride stored in the form of coarse blocks and ground finely before use is employed.

The reagents and the catalyst are heated in the liquid phase to a temperature of between 10 and 200C. and preferably between 20 and C. Several methods of working are possible; for example, the whole of the reagents may be heated to the desired temperature until the reaction is complete, or the organochlorosilane may be introduced gradually into a flask already containing compound (II) and the aluminium trichloride.

At the end of the period of heating, when the reaction is complete (the end of the reaction can be identified by disappearance of the organochlorosilane (ill) the constituents of the reaction mixture can be separated by any known method, for example, by fractional distillation. The fractions obtained may possibly contain, apart from the required product (I), small amounts of organosilicon compounds of various degrees of chlorination, as well as the diaryldimethylsilane (ll) starting material. The pure aryldimethylchlorosilane (I) can be obtained either by a second rectification, or vby any known chemical process, such as, for example, that described in French Patent Specification No. 1,466,546. llf it is desired to remove the more highlyv chlorinated impurities, a small amount of phosphoric acid and n-butanolmay be added to the mixture; these compounds form complexes with the most highly chlorinated derivatives and so make it possible to isolate the desired product in the pure state by distillation.

in order to avoid carrying aluminium trichloride into the distillates and the possibility of subsequent aluminium trichloride catalysed side-reactions, it is advantageous to complex the catalyst in the final mixture. This can be done by adding a ketone such as acetone, at a temperature of the order of,;for example, 20? to 25C. It is also possible to add analkali metal halide, such as sodium chloride, to the final mixture and to heat the mixture briefly. Y

The aryldimethylchlorosilanes (I) 4 are particularly useful in the field of organosilicon chemistry, because of their reactive chlorine atom which enables them to be converted into very many products, amongst which there may I be mentioned alkoxysilanes, hydrogenosilanes, aminosilanes, silicon-containing mercaptans and disiloxanes. Furthermore, the 1 aryldimethylchlorosilanes (I) can be employed, optionally after hydrolysis, as chain stoppers in polymerisation reactions.

- The Examples which follow illustrated the invention.

EXAMPLE 1 39.3 of diphenyldimethylsilane, 113 g. of dimethyldichlorosilane and y 4 g. of aluminium trichloride are introduced into a reaction flask, and

maintained at 80C. for 7% hours. After cooling, 3 g. of acetone are added and the aluminium chloride-acetone complex is filtered .off. Rectification under reduced pressure yields a fraction F, of boiling point so-91c.,

. at .rnm pressure weighing g. and containing percent of phenyldimethylchlorosilane (determined by chromatographic analysis).

0.3 g.of phosphoric acid and 4.1 g. of n-butanol are added to fraction F heated to C. After distillation under reduced' pressure, 1 a pure phenyldimethylchlorosilane fractionis' obtained weighing 43 I g. of boiling"po int- =.80-84C.-;at 16 mm pressure. The overall yield of phenyldimethylchlorosilane, relative to diphenyldimethylsilane, is 73 percent.

EXAMPLE 2 A mixture of 109 g. of dimethyldiphenylsilane, 1 16.5 g. of phenylmethyldichlorosilane and 4.6 g. of aluminium trichloride is kept at 100C. for 6 hours. After cooling,-2'.5 g. of acetone are added, the acetone-aluminium chloride complex is filtered off, and the filtrate is distilled to give fractions F of boiling point 8 1 .585.8

C.,at 1.9 mm pressure weighing 65 g., and containing 75.4 percent of dimethylphenylchlorosilane, and F of boiling point 84-107C., at 0.3 mm pressure weighing g. and containing 86.4 percent of methyldiphen- .ylchlorosilane. These various fractions are thereafter "treated as described in Example 1, to give pure dimethylphenylchlorosilane and pure methyldiphenylchlorosilane.

[EXAMPLE 3 A mixture of 106 g. of dimethyldiphenylsilane, 152 g. of diphenyldichlorosilane and 5.1 g. of aluminium trichloride is heated to 90C. for 5.% hours. After cooling, 3 g. of acetone are added, the resulting complex is filtered off, and the filtrate is distilled to give fractions 7 EXAMPLE 4 A mixture of 170 g. of dimethyldiphenylsilane, 108.7

g. of trimethylchlorosilane and 4.6 g. of aluminium trichloride is heated to 93C. for 6 hours 40 minutes. After cooling, 3' g. of acetone are added, the resulting complex is filtered off,- and the filtrate is distilled under reduced pressure to give fraction F, of boiling point 82.8-94C., at 30 mm pressure weighing 116.5 g. and

' containing 55 percent of vpherlyldirnethylchlorosilane and 39.8 percent of phenyltrimethylsilane. Rectification of fraction F gives fractions F,' of boiling point 56-57C. at 16 mm pressure weighing 43 g. and containing pure phenyltrimethylsilane, and F, of boiling point 8285C., at 16 mm pressure, weighing 61 g. and containing pure phenyldimethylchlorosilane.

EXAMPLE 5 A mixture of 113.2 g. of dimethyltolylphenylsilane,

129.1 g. of dimethyldichlorosilane and 4.8 g. of aluminium trichloride is heated to 87-88C. for 5 hours.

After cooling to about 25C., 3 g. of acetone are added,

the resulting complex is filtered off, and the filtrate is Air-Sii-Cl in which Ar represents a monovalent aromatic.

hydrocarbon radical, wherein a diaryldimethylsilane of the general formula Bile Ar-Si-Gl in which the radicals Ar, which may be identical or different, each represent a. monovalent aromatic hydrocarbon radical, is reacted. in the liquid phase at a temperature of between 20 and C, in the presence of aluminium trichloride, with'an organochlorosilane of the general formula v in which the symbols R,- which may be identical ordifferent, each represent a saturated or unsaturated, monovalent, hydrocarbon radical of aliphatic,

cycloaliphatic, aromatic or aralkyl nature, and n is 1 or 2. A process according to claim 1 wherein Ar represents an unsubstituted mononuclear hydrocarbon radical or a mononuclear hydrocarbon radical substituted by alkyl groups or chlorine atoms.

3. A process according to claim 2 wherein each Ar group in the diaryldimethylsilane is identical. i 4. A process according to claim 1 wherein R represents a saturated or unsaturated straight or branched chain aliphatic hydrocarbon radical containing up to six carbon atoms or a cycloalkyl or cycloalltnyl radical containing four to six ring carbon'atoms or a phenyl, phenylalkyl or alkylphenyl radical. I

5. A process according to claim 1 wherein n 2.

6. A process according to claim '1 wherein aluminium trichloride is present in an amount of 0.1 10 percent by weight based on the total weight of organosilicon reactants.

7. A process according-to claim 1 wherein after the reaction is completed a ketone is added to the reaction mixture to complex with the aluminium trichloride.

and pure C. in the presence of 0.5 5 percent by weight aluminium trichloride based on the combined weight of diaryldimethylsilane and organochlorosilane, acetone is added to the reaction mixture after completion of the reaction, the resulting acetone/aluminium trichloride complex is removed from the reaction mixture, phosphoric acid and n-butanol added to the reaction mixture and the reaction mixture thereafter distilled to give the aryldimethylchlorosilane as a distillate. 

2. A process according to claim 1 whereiN Ar represents an unsubstituted mononuclear hydrocarbon radical or a mononuclear hydrocarbon radical substituted by alkyl groups or chlorine atoms.
 3. A process according to claim 2 wherein each Ar group in the diaryldimethylsilane is identical.
 4. A process according to claim 1 wherein R represents a saturated or unsaturated straight or branched chain aliphatic hydrocarbon radical containing up to six carbon atoms or a cycloalkyl or cycloalkenyl radical containing four to six ring carbon atoms or a phenyl, phenylalkyl or alkylphenyl radical.
 5. A process according to claim 1 wherein n
 2. 6. A process according to claim 1 wherein aluminium trichloride is present in an amount of 0.1 - 10 percent by weight based on the total weight of organosilicon reactants.
 7. A process according to claim 1 wherein after the reaction is completed a ketone is added to the reaction mixture to complex with the aluminium trichloride.
 8. A process according to claim 1 wherein after the reaction is completed, phosphoric acid and butanol is added to the reaction mixture to complex any highly chlorinated derivatives.
 9. A process according to claim 1 wherein a diaryldimethylsilane selected from the group consisting of diphenyldimethylsilane and dimethyltolylphenylsilane is reacted with an organochlorosilane selected from the group consisting of dimethyldichlorosilane, phenylmethyldichlorosilane, diphenyldichlorosilane and trimethylchlorosilane in the liquid phase at 20* - 150*C. in the presence of 0.5 - 5 percent by weight aluminium trichloride based on the combined weight of diaryldimethylsilane and organochlorosilane, acetone is added to the reaction mixture after completion of the reaction, the resulting acetone/aluminium trichloride complex is removed from the reaction mixture, phosphoric acid and n-butanol added to the reaction mixture and the reaction mixture thereafter distilled to give the aryldimethylchlorosilane as a distillate. 